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Volvo 850 S/V70 Compressor Clutches

tony1963 on Sat October 27, 2007 9:10 AM User is offline

Country of Origin: United States

Greetings all,

In our shop, we have been changing AC compressors on Volvo 850 and the newer S/V70 series quite frequently. What we discover is that the clutch gets weak or bad and won't engage the compressor after 15-20 minutes of use. When it cycles, it doesn't reengage. After a cooling off period, it works for a while again.

The cost of the clutch exceeds the cost of a reman clutch/compressor assembly from our supplier. I have quite a few in the shop as cores and was wondering if anyone has ever "repaired" a bad clutch, particularly on this model.

Any ideas?

Grove Automotive Group, Inc.

An Alabama Corporation

Karl Hofmann on Sat October 27, 2007 11:31 AM User is offlineView users profile

Pop the clutch off and adjust the clutch gap by removing a shim..Problem is the compressor needs to come off in order to get the clutch off.

Never knock on deaths door... Ring the doorbell and run away, death really hates that!

2POINTautO on Sun October 28, 2007 12:38 AM User is offlineView users profile

Taking these compressors off is easy, it sounds like they are laying around the shop (cores). You should build into your troubleshooting technique a "compressor clutch COIL amp test" to see how many amps the coil is pulling. After some time you will learn on different compressors how many amps is a "GO or NO GO" reading.

Along with the "Air Gap" being too big as Karl mentioned, the "Coil" could be overheating, adding resistance and loosing magnatism also as a cause of your problems. At least with disassembly to adjust the air gap, you can do a visual inspection of the clutch disc to determine if you want to change the entire compressor, since that sounds like your cheapest option, that is strange, have you priced parts on some of these AC Forums.

Its good that you have soved up some cores for quick replacement option, hope you keep getting these Volvos in for some time to come, of course you know that the cores wont keep getting replaced as some of the compressors will be bad internally as well and not refurbishable by you, good luck finding cheaper "Quality" parts. Doesn't Volvo use GM AC systems or components, maybe that was Audi, been too many years???

Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

tony1963 on Sun October 28, 2007 7:15 AM User is offline

Volvo does not use GM parts in their AC systems.

Grove Automotive Group, Inc.

An Alabama Corporation

bohica2xo on Mon October 29, 2007 12:45 AM User is offline


The Volvo 850's used the DKS15CH compressors (Diesel KiKi) which are shim adjustable for clutch clearance.

Look HERE for the parts breakdown. Page 11 & 12 of that PDF show the typical DKS15CH compressor. Item 8 is the shim set.

Since this is a bench job, you can take the time to set the clutch gap down close to the minimum for longer life. Some books show .015 to .025 gap, others .010 to .022 You can safey set the gap as small as .003, as long as the clutch plate is square, and it does not drag or touch. Check the gap at 4 or 5 places around the diameter with a feeler gauge to be sure.

Clutch coils can only fail 3 ways:
1) Open circuit - no current flows, clutch does nothing.
2) Shorted turn-to-turn - resistance drops, clutch draws more current & overheats. Either the fuse blows, or the remaining windings fail & open circuit eventually.
3) Short to ground - the fuse usually blows.

The shim washers for adjusting the clutch do not come in fine increments .015 & .025 are the only ones as I recall. This leads to people using the high end of the book clearance, because the other choice reduces the clearance to below the .010 value in the book. You should go for the smallest gap that does not drag or rub.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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